This is the famous Black Virgin Mountain. It was home to a special US telecommunication site, a Monastery, and the Viet Cong Artillery. Tay Ninh and Dau Tang were located near it. Dau Tang being also the home of the Michelin Rubber Plantation and Tay Ninh the home of part of the 25th Inf Div and the 196th Lt Inf Bde.
If my memory serves me correct, that is Tay Ninh at the base of the mountain - correct me if I'm wrong. If I misspelled anything please forgive me.